(a) Technical Field
The present invention relates to a method for preparing pure graphene using chemical bonding between graphite oxide and metal oxide nanoparticles, and graphene and nanoparticles having a quasi metal oxide-graphene core-shell prepared therefrom.
(b) Background Art
Graphene, a miracle material, has a structure of one-atom-thick planar sheets of carbon atoms. Despite the rather short research period as compared to those for other nanocarbon materials such as carbon nanotube (CNT), fullerene or graphite, graphene is highly valued because of its excellent thermal conductivity and electron mobility and peculiar advantages such flexibility. Potential applications of graphene include the followings.
I) Graphene can replace the indium tin oxide (ITO) used in a transparent electrode of a light-emitting diode (LED), solar cell, or the like. With superior flexibility, it can be used in flexible electronic devices to greatly enhance lifetime and durability without affecting the device characteristics. In addition, graphene may be uses as an electrode material for secondary cells, supercapacitors, or the like.
II) With good thermal conductivity, graphene is esteemed as a new heat-sink material capable of solving problems in the manufacture of high-efficiency, high-brightness III-V GaN-based LEDs.
III) Further, superior dispersibility and good strength resulting from the 2-dimensional planar structure allow it to be used for carbon composite materials.
IV) Since the energy in graphene shows a linear relationship in the energy-wavenumber (E-k) diagram, it acts as if the effective mass of the electron (me*=∂2E/∂k2) is nearly 0. That is, it exhibits an effect as if the electron traveled fast like the massless photon. Accordingly, it has high potential as the next-generation transistor material for ultrafast electronic devices.
V) Besides, graphene can be used as a barrier film material because it has very low water permeability. Thus, it can be used as a barrier film material for flexible electronic devices and for packing and medical applications.
Thus, studies on the preparation of pure graphene are on the increase. The existing methods for preparing graphene include, in addition to the method of physically preparing graphene through exfoliation from graphite using a Scotch tape, a method of preparing graphene using carbon nanotube (CNT) [M. Terrones, Materials science: Nanotubes unzipped, Nature, 458, 845 (2009)], a method of growing graphene by chemical vapor deposition (CVD) [K. S. Kim et al., Large-scale pattern growth of graphene films for stretchable transparent electrodes, Nature, 457, 706 (2009); D. H. Lee et al., Versatile carbon hybrid films composed of vertical carbon nanotubes grown on mechanically compliant graphene films, Adv. Mater., 22, 1247 (2010)], and a method of chemical exfoliation from liquid phase [A. A. Green et al., Solution phase production of graphene with controlled thickness via density differentiation, Nano Letters, 9, 4031 (2009)].
However, the known methods are expensive and do not readily give pure graphene. Accordingly, there is a need of a simple method for preparing pure graphene.